Centrifugal fluid purifier



@cit. 18, 11949. 1. LANGMUIR CENTRIFUGAL FLUID PURIFIER Filed Sept. 25, 1945 Fig. l.

Inventor: Irving Langmuir",

His Attorney Patented Oct. 18, 1949 CENTRIFUGAL FLUID PURIFIER Irving Langmuir, Schenectady N. Y., assignor to General Electric Company, a corporation of New York Application September 25, 1945, Serial No. 618,532

The invention relates to fluid purifying apparatus, particularly centrifuge apparatus for removing fine particles from a gas or other fluid by the action of centrifugal force.

The principal object is to provide an improved high speed spinning cylindrical wall form of fluid purifying apparatus capable of subjecting particles carried in an annular column of fluid along the inner surface of the spinning cylindrical walls to an intense centrifugal field such as, for example, several thousand times that of gravity so as more effectively to deposit the fine particles on the spinning walls.

Another object is to provide an improved form of high speed multi-tubular spinning wall apparatus capable of purifying large volumes of air at a low cost and particularly adapted for removing fine particles such as those of tobacco smoke.

The fine smoke particles in a fluid such as air contained in any closed space normally tend to disappear mainly by gravity settlement according to equation:

where n is the number 'of smoke particles per cm., t is the time in seconds, V is the volume of the vessel in cm. v is the velocity in cm./sec. with which the particles fall in undisturbed air under the influence of gravity and A is the horizontal cross section of the vessel, or the projected area of the walls of the vessel on a horizontal plane.

3 Claims. (Cl. 233-17) This equation is based upon the assumption that there are sufilciently strong convection currents in the fluid to keep it well mixed at all times. However, if the fluid is made to move rapidly, for example, by rotating a fan within the vessel, the rate of disappearance of the smoke is not materially aifected until relatively high velocities are obtained. At very high velocities the'smoke particles may be diffused in appreciably increased-amount to the walls and be deposited even on vertical walls on which gravity settling cannot occur. Such diifusion is most rapid in the case of fine particles for the Brownian movement of these fine particles is much greater than that of large particles. The effect of the mechanical motion of the fluid increasing the smoke particle diffusion results from the fact that the fluid currents carry the smoke particles to within a fraction of a millimeter of the surface so that the smoke particles can diffuse the small remaining distance. Without such strong agitation there would be a relatively thick layer -2 or shield of quiet fluid near the surface through which the particles would have to diffuse.

If still higher velocities are used and the fluid is made to rotate at high speed in a cylindrical vessel by a rotor inside of it provided with radial vanes, then centrifugal force tends to force the heavier particles outward through the rotating fluid. .However, near the cylindrical walls the fluid is not rotating, being held by viscosity near the stationary surfaces. Thus as the particles slow up in their rotary motion before they reach the walls the centrifugal effect is greatly reduced, Consequently only relatively large particles of several microns diameter can be effectively removed by the centrifugal force produced by whirling a fluid in a stationary vessel.

In purifying air containing smoke in accordance with the principle of the present invention, the walls of the vessel through which the air is passed rotate at high speed so that smoke particles in the annular rotating sheet of air closely adjacent to the wall surfacesare exposed to the action of an intense centrifugal force. Thus the invention may be carried out in a simple form by rotating a cylinder at high speed about a central axis and the air from which the smoke is to be removed passed in a thin annular rotating sheet adjacent the inner surface of the cylinder in a direction parallel to the axis. Under these conditions the smoke is made to disappear according to the following equation where no is the number of smoke particles per cm. in the smoke entering the cylinder, n is the number per cm. in the smoke leaving the cylinder, R is the radius and a: the length of the cylinder in cm., (p is the rate of flow of gas through the cylinder in cm. per second, V is the velocity of fall of the smoke particles in in the centrifugal field which exists in the annular rotating sheet of air adjacent the inner surface of the rotating cylinder and in the simple form of apparatus described above, N is a number equal to 1. In general, N would represent the number of coaxial cylinders that are used for the collection of smoke.

Hence a further object of the invention is to provide an improved form of fluid purifying apparatus having a high speed rotor consisting of a nested series of thin coaxial cylinders of increasing radius spaced only slightly apart and interconnected together so as to provide a multiplicity of closely adjacent annular walls between which a substantial flow of fluid in thin coaxial elm/sec.

annular columns may be passed and thereby subject to an extremely high centrifugal force.

Further objects and advantages of the invention will appear in the description of the accompanying drawings in which Fig. l is a longitudinal sectional view of a high speed spinning multitubular cylindrical wall fluid purifying apparatus embodying the improvements of the present invention in a preferred sectional view along the line 2-2 of Fig. 1 showing more clearly the details of construction.

As shown in Fig. 1 the improved fluid purifying device is provided with a stationary outer shell ll interconnecting the inlet casing II and the outlet casing l2 through which the fluid or gas to be purified is circulated. The inlet casing II is provided with an offset inlet pipe connection I! and the outlet casing 12 is provided with a similar outlet pipe connection II. A drive shaft I5 is rotatably mounted in the bearing l6 and I1 formed centrally in the corresponding inlet and outlet casings II and I2. The drive shaft I5 is connected to be rotated at high velocity by an electric motor or other suitable motive power, not shown, through the driving coupling l8.

The inulti-tubular rotor l9 consisting of a plurality of nested closely adjacent cylinders 20, each formed of relatively thin material, is mounted for rotation with the shaft I5 by means of the two suitably formed mounting spiders 2| and 22, preferably with each of the till cylinders 20 welded to each spider so as to insure rigidity of the multi-tubular rotor structure. The innermost one of the cylinders 20 with the spider hubs 21a and 22a welded to the ends thereof forms an elongated axial cylindrical drum 23 surrounded by the adjacent nested coaxially aligned cylinders 20 so as to provide concentric thin annular flow passages 20b extending between the opposite ends of rotor' l9. Each of the mounting spiders 2|, 22 likewise is rigidly secured :to the shaft 15, preferably by welding with the periphery of each spider at the opposite ends of the rotor extending into a substantially fluidtight running fit with the sealing rings 24 provided for sealing the opposite ends of the multi-tubular rotor IS with respect to the inlet and outlet casings H and I2.

As more clearly shown in Fig. 2, when used for purifying air or other gas the inlet casing l I may be provided with a series of expansion vanes or blades 25 which cooperate with the corresponding rotating expansion blades 25 carried by the mounting spider 2| so as to expand the gas admitted through the inlet pipe [3- into the inlet casing H before the gas is passed in thin annular columns through the multiple annular passages between the coaxial cylinders 20.

The mounting spider 22 at the outlet end ofrotor Is also may be provided with a series of blades 30 extending outwardly at a suitable angle within the outlet casing l2 so as to produce a recompression of the gas before it is exhausted through the outlet pipe ll. Furthermore the blades 30 and the outlet casing l2.can also serve as centrifugal fluid flow inducing means for producing a flow of gas in thin multiple annular sheets through the hollow rotor l9 formed by shaft and the several coaxial cylinders 20.

In operation when the drive shaft l5 of rotor I9 is driven at high speed, the centrifugal blower action produced by blades 30 serves to reduce the pressure within the outer shell l0 so that the gas will be drawn into the inlet casing I I through the inlet pipe I3. The expansion of the incoming form, and Fig. 2'is a cross gas through the blades 25 and delivers some power to the rotor I! which at least can partly compensate for the power used in recompressing the gas at the opposite end. In this'way the gas such as air enters and leaves the rotor I! with relatively low velocity and within the rotor is under subatmospheric pressure and has a high velocity of rotation but not as great a longitudinal velocity (in the direction of the axis of the rotor). Thus such a construction can increase the overall efllciency of the device.

If desired, the fluid may be delivered through the inlet pipe connection I! at sufllcient pressure and velocity such thatthe reaction produced by directing the fluid through vanes upon blades 26 will provide all the power required for spinning the rotor I 9 and the fluid then allowed to exhaust axially through the rotor I9 without the provision of any recompression blades". Furthermore, it will be understood that other suitable means for obtaining the axial flow of fluid in thin concentric rotatable columns through the multiple annular passages between the concentric cylinders 20 and for spinning the rotor 19 may be employed if desired.

With a rotor consisting of a series of thin 00- axial cylinders of increasing radius spaced a few millimeters apart, for example, with arotor having 10 coaxial cylinders with an average radius R=10 cm. and the length of the cylinders z=30 cm., we find that Equation 2 becomes Now if we consider air as containing smoke consisting of spherical particles having a density 0.9 gram per cm. we can calculate from Stokes law that v=1.06 10r}(g/a1) cm./sec. (4)

Where the acceleration g is given by:

where v is equal to the revolutions per second and gi=980 the normal acceleration of gravity and Ts is the radius of the smoke particles. If we consider that the rotor is revolving at 5000 a. P. M.

or a=83 R. P. S., we obtain q=2.77 10 or 2850 times gravity. Thb gives for smoke particles of radius 1's, o=3.0 X 10 1",.

If we consider smoke particles r-=3Xl0- cm. this gives v=2.'7 cur/sec. A smoke with this particle size is most diflicult to remove from air by a fllter and yet with this high centrifugal force in a device having the construction described above the particles can be made to move 2.7 cm. per second, nearly 3000 times their normal speed. Introducing this value of v in Equation 3 we obtain for the effectiveness of this centrifuge for removing this smoke larger numbers of coaxial cylinders. Higher speeds of rotations may also well be used. The smoke particles deposited upon th cylinders 20 may be readily removed by periodic flushing with water or other suitable solvent.

5 What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fluid purifying device having in combination a multi-tubular rotor comprising an axial cylindrical drum and a plurality of adjacent side wall of the corresponding cylinder.

2. A gas purifying device having in combination a multi-tubular rotor comprising a plurality of coaxial closely spaced substantially imperiorate cylinders formin thin annular flow passages extending between the ends of said rotor,

means including an outlet casing having a substantially fiuidtight running seal with one end ot said rotor and blades carried by said rotor inside said casing and extending radially from the corresponding end of said passages for producing a flow oi gas in coaxial annular columns through said passages, and means for spinning said rotor to rotate said gas columns at high velocity to establish high centrifugal forces therein for dii'- afusing fine particles from each of said to the outer wall of the corresponding passage.

'3. -A centrifuge device for removing smoke-particles from air having in combination amulti-tubular rotor comprising a plurality of nested coaxial closely adjacent and substantially imperioin the rotating fluid inside each of said cylinders for diffusing fine particles therefrom to the inrate cylinders, said cylinders forming a plurality of concentric thin annular passages extending between the opposite ends of said rotor, means including a casing at each end of said rotor and having a substantially fluidtight running sealing therewith for producing a flow of air in nested thin annular columns through said passages, and means for spinning said rotor to rotate said air columns at high velocity to establish high centrifug-al forces therein adjacent the inner wall of each or said cylinders for difiusingfine smoked particles from the corresponding air column thereon.

- IRVING LANGMUIR.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name a Date;

403,701 See]: May 21, 1889 582,317 Shaw et a1. May 11; 188'! 587,171 Beach Julyi2'l, 1897 717,963 Bardelle Jan. 6,1903 1,057,613 Baldwin Apr. 1, 1918 1,061,656 Black May 13, 1913 1,896,180 Lindequist Feb. 7. 1933 2,104,683 Van Rosen Jan. 4, 1938 2,126,481 Lapp et a1. Aug. 9, 1938 FOREIGN PATENTS Number Country Date 257,313 Germany May 4, 1913 Germany 570,285 Feb. 21. 19a:

Certificate of Correction Patent No. 2,485,390 October 18, 1949 IRVING LANGMUIR It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 60, Equation 6, for n=n e read n=n e";

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice. Signed and sealed this 7th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant ammz'uiomr of Patents. 

